linux-kernel - [PATCH][next] ipmi: ipmb: Fix off-by-one size check on rcvlen

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Message-Id: <20211005151611.305383-1-colin.king@canonical.com>
Date:   Tue,  5 Oct 2021 16:16:11 +0100
From:   Colin King <colin.king@...onical.com>
To:     Corey Minyard <minyard@....org>,
        openipmi-developer@...ts.sourceforge.net
Cc:     kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH][next] ipmi: ipmb: Fix off-by-one size check on rcvlen

From: Colin Ian King <colin.king@...onical.com>

There is an off-by-one bounds check on the rcvlen causing a potential
out of bounds write on iidev->rcvmsg. Fix this by using the >= operator
on the bounds check rather than the > operator.

Addresses-Coverity: ("Out-of-bounds write")
Fixes: 0ba0c3c5d1c1 ("ipmi:ipmb: Add initial support for IPMI over IPMB")
Signed-off-by: Colin Ian King <colin.king@...onical.com>
---
 drivers/char/ipmi/ipmi_ipmb.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/char/ipmi/ipmi_ipmb.c b/drivers/char/ipmi/ipmi_ipmb.c
index b10a1fd9c563..77ebec4ed28e 100644
--- a/drivers/char/ipmi/ipmi_ipmb.c
+++ b/drivers/char/ipmi/ipmi_ipmb.c
@@ -192,7 +192,7 @@ static int ipmi_ipmb_slave_cb(struct i2c_client *client,
 		break;
 
 	case I2C_SLAVE_WRITE_RECEIVED:
-		if (iidev->rcvlen > sizeof(iidev->rcvmsg))
+		if (iidev->rcvlen >= sizeof(iidev->rcvmsg))
 			iidev->overrun = true;
 		else
 			iidev->rcvmsg[iidev->rcvlen++] = *val;
-- 
2.32.0